A framework for a dental prosthesis (FIG. 1) (2) is the metal base structure of the prosthesis (1). It is supported by oral implants (4) placed in the jawbone (5) or by remaining teeth. Such framework is fixed to the jaw by screwing it on the implants or by cementing it on the remaining teeth. The framework supports the missing teeth (3) which are attached on the support surfaces on top of the framework. The prostheses are patient specific and have to meet strict requirements of accuracy to reach an optimal fit at the prosthesis-implant or prosthesis-tooth junction. To distribute forces evenly and to avoid high stresses in the jawbone causing the oral implants to loose and to diminish the risk for colonization of bacteria resulting in infection and eventually bone loss, a good passive fit between the framework and the implants or the remaining teeth and severe fit criteria below 40 μm are necessary. Because the framework can replace all teeth and because the framework connects the occlusal surfaces of the missing teeth with the oral implants, the framework is larger and more massive in comparison with other dental applications like crowns and small bridges.
The conventional commercial systems to produce these frameworks are based on a manual design of a physical model of the framework and a production by means of lost wax casting or milling. Although these processes lead to high precision, they are time consuming and inefficient. The lost wax method is a lengthy and labour-intensive process and comprises many manual steps (fabricating the wax pattern, embedding the wax pattern, burning out the wax material, metal casting, post-processing). By digitizing the manual design and using CAM-instructions, the frameworks can be produced through a milling process. However, this milling process is also time consuming because of the lengthy calculation of the tool paths and because of the lengthy manual finishing needed to obtain an accurate fit of the framework. Moreover, most of the material is wasted and spatial restrictions limit the production of complex shapes.
WO2004075771 provides a method for the digital design of a model of the framework. This digital model is subsequently used in rapid prototyping techniques to generate moulds, which can be used for indirect production of the final framework. Alternatively, it is proposed in WO2004075771 to use said digital model of the framework together with CAM-instructions to directly produce the framework by automated milling.
The present invention describes for the first time the direct rapid manufacturing of medically acceptable frameworks produced using computer controlled selective laser powder processing techniques (SLPP). The accuracy of the biocompatible frameworks meets the required severe fit criteria and their high density guarantees highgrade mechanical properties which can resist the complex and heavy loading conditions and long term wear to which a large, implant-supported framework is subjected. Selective laser powder processing techniques have the advantage over conventional methods for the production of dental frameworks that they allow to fabricate complex shapes without the need for lengthy manual pre- or post-processing and have the possibility of mass customization. As Selective laser powder processing techniques allow to produce many different geometries in a single production run, many different frameworks, adapted to the respective patient geometries and requirements, can be produced at the same time without manual intervention.